CHARACTERIZATION OF COPPER ZIRCONIA CATALYSTS PREPARED BY AN IMPREGNATION METHOD

Copper/zirconia catalysts were prepared by an impregnation method and were characterized by UV-visible-near-infrared (UV-VIS-NIR) spectroscopy, X-ray diffraction (XRD), differential thermal analysis (DTA) and temperature-programmed reduction (TPR). It was concluded that copper-ammine complexes held on the surface of the zirconia support exist in three different states, viz., isolated and clustered copper(II) ions and tetraamminecopper (II) nitrate. These precursor species were transformed into bulky copper (II) oxide through highly dispersed copper (II) oxide at various temperatures, which depend on the calcination temperatures of the catalysts and the zirconia supports. In the TPR experiments, two TPR peaks were observed at 493 K (peak I) and 515-613 K (peak II). In conjunction with the observations by UV-VIS-NIR and XRD, it was concluded that highly dispersed copper(II) oxide and bulky copper (II) oxide were reduced to metallic copper, giving peaks I and II, respectively. The relative amounts of these precursor species were found to depend strongly on the conditions of preparation of both catalysts and supports. © 1990.